JPH0410043B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to reinforced coated optical fibers. Prior Art Optical fibers are often used under harsh conditions when used, for example, as optical communication transmission lines, so they are required to have excellent mechanical properties and low transmission loss. For this reason, conventionally, for example, as shown in FIG. 1, a plastic buffer layer 2 (primary coating) is formed on the outer peripheral surface of an optical fiber 1 consisting of a core and a cladding, and then a buffer layer 2 (primary coating) is formed.
A reinforced coating layer 3 made of thermoplastic resin is provided on the outer peripheral surface of the
By forming a (secondary coating), a reinforced coated optical fiber was constructed. However, reinforced coated optical fibers with such a structure do not have very good mechanical properties, and the linear expansion coefficients of glass and resin differ by one to two orders of magnitude, which causes large stress to be placed on the optical fiber due to temperature changes, causing the optical fiber to deteriorate. In some cases, micropending occurred in the glass constituting the device, resulting in increased transmission loss. For this reason, recently, as shown in FIG. 2, a large number of low-pink glass fibers 41 are attached vertically to the outer peripheral surface of the buffer layer 2, and the thermosetting resin 42 impregnated into the fibers 41 is heated. The reinforcing coating layer 4 is formed by heating by means. In the thus obtained reinforced coated optical fiber, since the linear expansion coefficient of the glass fiber 41 is small, as the content ratio of glass fiber increases, the linear expansion coefficient of the reinforced coat layer 4 becomes lower than that of the optical fiber 1. The coefficient of linear expansion becomes close to that of the optical fiber 1, and therefore the difference in expansion and contraction between them becomes small, so there is no risk of large stress being caused to the optical fiber 1 due to temperature changes. However, in the reinforced coated optical fiber shown in Figure 2, it is necessary to use a considerable amount of glass fiber in order to sufficiently reduce the linear expansion coefficient of the reinforced coat layer, which makes it difficult to reduce the thickness or The flexibility is impaired, and since a large amount of glass fiber is used, the resin becomes brittle and there is a high risk of peeling at the interface between the resin and the glass fiber or cracking the resin. In addition to these drawbacks, there was also the problem that it was difficult to carry out production at high efficiency. The reason for this is that reinforced coated optical fibers are produced by passing optical fibers and resin-impregnated glass fibers through a heating device with an electric heater or the like and curing the resin, but thermosetting resins have a low thermal conductivity. This is because it is difficult to heat-cure the resin in a short time because the heat capacity of the glass fiber is poor and the heat capacity of the glass fiber is large.
Furthermore, the manufacturing equipment required equipment such as a feeding device for long glass fibers, a heating device for thermosetting, or a liquid tank for thermosetting resin, making the manufacturing equipment complicated and expensive. . Purpose of the Invention The present invention has been made under these circumstances, and has excellent mechanical properties such as maintaining transmission characteristics, having a thin structure, being highly flexible, and having high tensile strength. It is an object of the present invention to provide a reinforced coated optical fiber that can be produced with high efficiency. Summary of the Invention The present invention is characterized in that a reinforcing coating layer made of a thermoplastic resin containing a large number of whiskers is formed on the outer peripheral surface of the buffer layer using single-crystal microfibers called whiskers. Embodiments Embodiments of the present invention will be described below with reference to the drawings.
A reinforced coated optical fiber according to an embodiment of the present invention includes:
As shown in FIG. 3, a reinforcing coating layer 5 is provided on the outer peripheral surface of a buffer layer 2 covering the optical fiber 1, and this reinforcing coating layer 5 includes a large number of whiskers each oriented in the longitudinal direction of the optical fiber 1. The thermoplastic resin 7 contains 6. The whiskers herein are single-crystal microfibers made of potassium titanate, silicon carbide, silicon nitride, polyoxymethylene, or the like. When using whiskers, one type, for example, a whisker made of potassium titanate may be used alone, or two or more types may be used in combination, such as a whisker of potassium titanate and a whisker of silicon carbide. However, it is more preferable to use a whisker made of an inorganic material such as potassium titanate or silicon nitride, which has a coefficient of linear expansion close to that of the glass constituting the optical fiber. An example of a whisker is the white needle-like crystals of potassium hexatitanate (K ₂ O.6TiO ₂ ).These are fine particles with an average fiber length of 10 to 20 μm and a fiber diameter of 0.2 to 0.5 μm. The compatibility is also extremely good. The content ratio of whiskers 6 in the reinforcing coating layer 5 is preferably 2 to 60% by weight in order to achieve a sufficient reduction in the coefficient of linear expansion.
More preferably 10 to 40% by weight. Regarding the formation of the reinforcing coating layer 5, the whiskers 6 are kneaded into the thermoplastic resin 7 in advance and made into pellets, and this is coated on the outer peripheral surface of the buffer layer 2 to prevent scattering of whiskers. This is preferable from the viewpoint of uniformity and environmental hygiene. Furthermore, although the present invention is not limited to oriented the whiskers 6 in the length direction of the optical fiber 1, oriented the whiskers in the length direction leads to a further reduction in the linear expansion coefficient of the reinforcing coating layer. It is preferable in this respect. A state in which the whiskers 6 are oriented in the longitudinal direction of the optical fiber 1 can be easily obtained by extruding and coating the resin containing the whiskers at a drawdown ratio of about 10 times using an extruder. The thermoplastic resin 7 is made of polyester resin, polyamide resin, polyacetal resin, etc., and is appropriately selected based on required properties in addition to linear expansion coefficient. Next, a specific example of the present invention will be described in comparison with one that does not contain whiskers. <Specific example 1> Coating the optical fiber with a buffer layer and reducing the outer diameter to 0.4 mmφ
Thermoplastic nylon 12 containing 5% by weight of potassium hexatitanate whiskers was laminated on the outer peripheral surface of the buffer layer, and this was extruded and drawn down at a stretching rate of 20 times to form a reinforced coating layer, and the outer diameter was 0.9. A reinforced coated optical fiber of mmφ was obtained. This will be referred to as "optical fiber 1". <Specific example 2> The whisker content of potassium hexatitanate
A reinforced coated optical fiber of the same size was obtained in exactly the same manner as in Example 1, except that the amount was 10% by weight. This will be referred to as "optical fiber 2". <Comparative Example> A reinforced coated optical fiber having the same dimensions was obtained in exactly the same manner as in <Specific Example 1> except that the above-mentioned whiskers were not contained in nylon 12. This will be referred to as the "comparison optical fiber." The results of examining the above optical fibers 1 to 3 in terms of tensile strength, molding shrinkage rate, linear expansion coefficient, and molding state are shown in the following table.

[Table] As can be seen from this table, resins containing whiskers have a lower
It has high tensile strength, and low mold shrinkage and linear expansion coefficient. Further, there was no roughness on the resin surface, and no interfacial peeling that would cause cracks between the resin and whiskers was observed. Here, the reinforced coated optical fiber of the present invention is compared with a conventional reinforced coated optical fiber using longitudinally attached long glass fibers and a reinforced coated optical fiber using glass microfibers instead of whiskers. To explain this, when long glass fibers are used vertically, unless the content of long glass fibers in the reinforcing coating layer is 60 to 80%, a reinforcing coating layer with a low coefficient of linear expansion cannot be obtained. However, in the present invention, the linear expansion coefficient of the reinforcing coating layer can be lowered without vertically attaching glass fibers, so it has more plasticity than the conventional one, and the thickness of the reinforcing coating layer can be reduced. It is also possible to make it smaller. In addition, when glass microfibers are used, surface roughness of the reinforcing coating layer becomes a problem, which becomes a major problem especially when thinning the wall. Whiskers are 1/50 to 1/2 the size of glass microfibers. 100, so there is no surface roughness during molding. Also, when comparing the tensile strengths, the reinforcing coating layer using whiskers has a higher tensile strength. Further, in the present invention, as shown in FIG. 4, two optical fibers 1 each having a buffer layer 2 formed on their outer peripheral surfaces are arranged, and the reinforcing coating layer 5 is formed on their outer peripheral surfaces to form two optical fibers. Alternatively, as shown in FIG. 5, a buffer layer 2 may be formed on the outer peripheral surface of two optical fibers 1 so that they are integrated, and the outer periphery of this buffer layer The reinforcing coating layer 5 may be formed on the surface. Effects of the Invention As described above, according to the present invention, since whiskers, which are single-crystal microfibers, are used in the reinforcing coating layer, the linear expansion coefficient of the reinforcing coating layer is reduced, suppressing stress on the optical fiber due to temperature changes. This can prevent an increase in transmission loss. Furthermore, it is possible to obtain a reinforced coated optical fiber having a high tensile strength, high flexibility, and excellent mechanical properties even though the reinforced coating layer has a thin structure. Furthermore, since the whisker-containing resin is a thermoplastic resin, it is possible to significantly increase the line speed, which was previously a problem due to the curing time caused by the use of thermosetting resins, resulting in high efficiency. can be produced. Since the reinforced coated optical fiber of the present invention can be manufactured by a general extrusion method, it requires a heating device for thermosetting the resin, a feeding device for long glass fibers, and a thermosetting resin. Since a liquid tank or the like is not required, manufacturing can be carried out using simple equipment.

[Brief explanation of drawings]

1 and 2 are front views showing a conventional reinforced coated optical fiber, FIG. 3 is a front view showing a reinforced coated optical fiber according to an embodiment of the present invention, and FIGS.
FIG. 5 is a front view of reinforced coated optical fibers according to other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Optical fiber, 2... Buffer layer, 5... Reinforced coating layer, 6... Whisker, 7... Thermoplastic resin.

Claims (1)

[Scope of Claims] 1 Consists of an optical fiber covered with a buffer layer and a reinforced coating layer formed on the outer peripheral surface of the buffer layer, and this reinforced coating layer is made of a thermoplastic resin containing a large number of whiskers. A reinforced coated optical fiber characterized in that: 2. The reinforced coated optical fiber according to claim 1, wherein the whisker content in the reinforced coat layer is 2 to 60% by weight.